Testing of climate simulations for the highlands of Lesotho (southern Africa) during the Last Glacial Maximum with proxy-data from phylogeography, geomorphology and palaeobiological isotope geochemistry

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The highlands of Lesotho represent the most important “water tower” of the largely semi-arid southern Africa. The impact of climate change on water resources is discussed controversially. In climate models a relatively small increase in temperature leads to a significant decrease in precipitation. Interestingly, climate simulations of the Last Glacial Maximum (LGM) hint at dry climate as well but under notably lower temperatures than today. This conclusion is partly derived from presumedly small-scale glaciation of the highlands and partly from lake sediment and speleothem archives, which are located in South Africa and are difficult to relate with Lesotho because of different oro- and hydrographic settings. Except for certain cultural layers, there are no sedimentary archives of LGM age and supposed (peri-) glacial landforms have not yet been dated. Archaeological excavations at the Sehonghong Shelter exhibited LGM-layers which contained fish remains, providing initial evidence that at least certain rivers of the highlands must have been active. The main hypothesis which shall be tested here is that the LGM-climate of the highlands of Lesotho was significantly less dry and less cold than generally assumed. Own data suggest that such a paradigm change likely applies to the Kalahari where a northern-southern-hemisphere climate seesaw becomes apparent. The presumption thus is that the glaciers in the Lesotho highlands were not extended (or even absent) because the climate was too warm and not because it was too dry. A phylogeographic study of riverine snails of the highlands will allow to show whether the snails lived there during the LGM and consequently the river systems were hydrologically active at a large scale. Geomorphological research will focus on suggested (peri-) glacial landforms and alternative interpretations will be considered. Stable isotope analyses of fish bones from LGM-cultural-layers will be compared with corresponding data from modern fish and temperature differences will be tested.